One piece sealed unit - no base required for mountingFits standard 3" spaced mounting holesEpoxy resin coated solid state circuitryPower connection is made via two wires that exit the back of light at the center. White wire is ground, black is positiveAvailable in Red and Amber with colored or clear lensPerfect LED upgrade for RVs using marker lights with 3" spaced mounting holes.We run this light on our 2010 Arctic Fox 811 truck camper - it's an exact fit